The present invention relates generally to pericardial enhancement, and more particularly to methods and systems for modifying the pericardium to reduce or eliminate remodeling of the heart for patients suffering from or at risk of heart failure.
A common form of heart disease involves cardiac dilation. Ventricular dilatation, for example, increases the load on the heart and decreases cardiac efficiency, producing symptoms of congestive heart failure. The ventricular walls grow thinner and more vulnerable as a result of ventricular dilatation and associated increase in wall stresses.
Healthy pericardium provides a constraint around the myocardium to prevent dilatation of the chambers of the heart. For patients suffering from or at risk of heart disease, the constraining forces of the pericardium may be inadequate to prevent dilatation of the chambers of the heart. The pericardium may decrease in rigidity and become excessively compliant, or the natural restraining capability of the pericardium may simply be inadequate to overcome the pressure produced by the cardiac dilation.
Cardiac reinforcement devices have been proposed for treating heart dilation. For example, U.S. Pat. No. 5,702,343 discloses a cardiac reinforcement device having a bio-compatible jacket to be placed over the epicardial surface of the heart to constrain cardiac expansion. U.S. Pat. No. 5,800,528 discloses a passive girdle to be wrapped around a heart muscle. The girdle is formed of unattached, linked loops designed to conform to the size and shape of the heart and to constrain the dilatation during diastole. U.S. Pat. No. 5,603,337 is directed to cardiomyoplasty in which a skeletal muscle is grafted around the heart. U.S. Pat. No. 4,536,893 discloses a device having expandable pumping chambers for receiving a pumping fluid to compress the myocardial wall.
Other cardiac muscle wraps are disclosed in Eli R. Capouya et al., xe2x80x9cGirdling Effect of Nonstimulated Cardiomyoplasty on Left Ventricular Function,xe2x80x9d 58 Ann. Thorac. Surg. 867-71 (1993); David A. Kass et al., xe2x80x9cReverse Remodeling from Cardiomyoplasty in Human Heart Failure,xe2x80x9d 91 Circulation 2314-18 (May 1, 1995); Mikhail Vaynblat et al., xe2x80x9cCardiac Binding in Experimental Heart Failure,xe2x80x9d 60 Ann. Thorac. Surg. 81-85 (1997); and Joong Hwan Oh et al., xe2x80x9cThe Effects of Prosthetic Cardiac Binding and Adynamic Cardiomyoplasty in a Model of Dilated Cardiomyopathy,xe2x80x9d 116 J. Thorac. Cardiovasc. Surg. 148-53 (1998).
The use of radio frequency (RF) energy to induce heat in collagen containing tissue to alter collagen in tissue is known. For example, U.S. Pat. No. 5,458,596 discloses an orthopedic apparatus for delivering RF energy to ligaments, joint capsules and connective tissue. U.S. Pat. No. 5,785,705 discloses an RF ablation apparatus for controlled depth ablation of soft tissue.
Heat-induced shrinkage of collagen tissue has been used for various treatments in the heart. For example, PCT Publication No. WO 98/26738 discloses treating myocardial infarction by selectively heating the infarct scar. U.S. Pat. No. 5,928,224 discloses using heat and/or applying pressure to treat infected or damaged heart valve tissue. Other applications of heat-induced treatment include shrinking the chordae tendinae (WO 98/35638), closing or abrading the patent foramen ovale (WO 99/18871, WO 99/18870, WO 99/18862, U.S. Pat. No. 5,919,200), modifying the collagen fibers of the vein (WO 98/32367), and closing the ductus arteriosus (U.S. Pat. No. 5,827,268).
The present invention is generally directed to methods and systems for treating patients suffering from or at risk of heart failure. The invention modifies the pericardium to treat heart failure of the type wherein constraining forces of the pericardium on the heart are inadequate to prevent remodeling involving geometric alteration of the heart. The pericardium is enhanced by restoring, increasing, or improving its ability to restrain the heart and prevent dilation of the chambers of the heart. Specific embodiments of the invention cause stiffening, strengthening, tightening, reshaping, and/or shrinking of the pericardium to enhance the restraining and supporting capability of the pericardium around the heart.
The pericardium includes collagen-containing connective tissue. Collagen fibers shrink and tighten when elevated in temperature. This molecular response to temperature elevation is believed to be the result of rupture of the collagen stabilizing cross links and immediate contraction of the collagen fibers to about one-third of their original linear dimension. In addition, the caliber of the individual fibers increases greatly, over four fold, without changing the structural integrity of the connective tissue.
An aspect of the present invention is directed to a method for treating patients suffering from or at risk of heart failure of the type involving inhibiting or preventing remodeling of the heart, for example, by placing an elastic or inelastic constraint surrounding at least a part of the heart. The improvement includes modifying the pericardium under conditions to inhibit remodeling of the heart.
In some embodiments, modifying the pericardium includes heating at least a portion of the pericardium under conditions that shrink collagen within the pericardial tissue while retaining tissue viability. The pericardium may be heated in a pattern of spaced-apart lines in a grid. Alternatively, the entire pericardium may be heated. Selective heating may be performed, for example, below the AV groove or in a region overlying the left ventricle.
In a specific embodiment, the pericardium is heated by contacting the pericardial tissue with a probe that applies RF energy to the pericardial tissue. The RF energy may be applied in a monopolar manner or a bipolar manner. The probe may be placed in contact with the pericardial tissue on the outside of the pericardium or from within the pericardial space. When the pericardium is heated from the outside, the fat on the outside of the pericardium is preferably first removed by mechanical abrasion, thermal ablation, suction, chemicals, or the like.
In another embodiment, at least a portion of the pericardium is conductively heated by placing a heating element in contact with or in close proximity to the pericardial tissue and circulating a heated fluid through the heating element. The heating element will preferably contact the entire area to be reinforced.
In another embodiment, the pericardium is modified by applying a chemical to reduce compliance of the pericardium. The chemical may include glutaraldehyde. The chemical may be removed from the patient substantially contemporaneously with the application of the chemical.
In yet another embodiment, modifying the pericardium includes plicating the pericardium, for example, by suturing or clipping.
A target region of the pericardium that is to be modified may be isolated by anchoring a portion of the pericardium surrounding the target region to the myocardium. Suturing or clipping may be employed in anchoring the portion of the pericardium to the myocardium.
If an anastomosis site is present, a ring of the pericardium may be coupled with the myocardium around the anastomosis. The coupling may involve attaching the ring of pericardium to an annular piece of biomedical material and attaching the annular piece of biomedical material to the myocardium around the anastomosis.
Certain embodiments of the invention involve accessing a region of the pericardium for treatment. The pericardium may be accessed, for example, by surgically opening the patient""s chest, forming an intercostal incision, or forming a subxiphoid access channel, or transvascularly via the venous system.
The pericardium may be treated while the heart remains beating or when the heart is stopped.
In accordance with another aspect of the invention, a method for treating patients suffering from or at risk of heart failure includes providing a device having a heating member, and placing the heating member in contact with or in close proximity to the pericardium of the heart. Energy is supplied to the heating member to cause heating of the pericardium under conditions and for a time selected to reduce or eliminate remodeling of the heart.
In one embodiment, the heating member includes an electrode and RF energy is applied through the electrode to the pericardium. In another embodiment, the heating member includes a circulation path and a heated fluid is circulated through the circulation path for heating the pericardium.
The device may include a fluid delivery port for introducing a chemical to the pericardium to reduce compliance of the pericardium. The device may further include a suction port for withdrawing the chemical introduced to the pericardium.
In a method for treating patients suffering from or at risk of heart failure of the type involving provision of constraint around the heart wherein constraining forces of the pericardium around the heart are inadequate to prevent remodeling of the heart, another aspect of the invention is directed to an improvement comprising modifying the pericardial tissue of the pericardium in a manner sufficient to inhibit remodeling of the heart while retaining viability of the heart.
In one embodiment, modifying includes introducing a stiffening chemical to stiffen the pericardium.
In another embodiment, modifying includes shrinking at least a portion of the pericardium. Shrinking may include applying thermal energy to the pericardium under conditions that shrink collagen within the pericardial tissue while retaining tissue viability. Shrinking may include tensioning of the pericardium to restrain the heart.
Another aspect of the invention is directed to a device for treating the pericardium. The device includes a heating member configured to be placed in contact with or in close proximity to the pericardium. A source of energy is coupled with the heating member for providing energy to the heating member to cause heating. The heating member includes a fluid delivery port, and a fluid delivery line extends from the fluid delivery port that is configured to be fluidicly coupled with a source of chemical for introducing the chemical through the fluid delivery port to the pericardium. The device may include a suction line extending from a suction port and being configured to be fluidicly coupled with a vacuum source for withdrawing through the suction port the chemical introduced to the pericardium. In a specific embodiment, RF energy is applied through electrodes provided in the heating member to the pericardium to heat the pericardium.
In accordance with another aspect of the invention, a kit is provided for treating patients suffering from or at risk of heart failure. The kit includes a member configured for modifying the pericardium. In specific embodiments, the member for modifying the pericardium may include a heating member for heating at least a portion of the pericardium, a fluid delivery member for delivering a fluid to the pericardium, and/or a plicating member for plicating the pericardium. The kit further includes instructions for use according to any of the methods set forth above. The kit may optionally further include a package for holding at least the member for modifying the pericardium, and usually the instructions for use. Exemplary packages include boxes, trays, pouches, tubes, and the like. In some embodiments, at least a portion of the member for modifying the pericardium will be maintained sterilely within the package. Optionally, devices for accessing the pericardium may be included. Further, optionally, when a fluid delivery member is provided as a member for modifying the pericardium, one or more chemicals may be included for use with the fluid delivery member.